VISVESVARAYA TECHNOLOGICAL UNIVERSITY BELGAUM – 590018

“Large-Area Capacitance Active Touch Panel Using the Method of Pulse Overlapping Detection”

Ramya R.

(1RL09EC063)

Under the Guidance of

Mr. Harish S.

Asst prof, dept of ECEDEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

R.L.JALAPPA INSTITUTE OF TECHNOLOGY

(Affiliated to VTU, Belgaum and Recognized by AICTE, New Delhi)

DODDABALLAPUR– 561203

2012-2013

Abstract

A active touch panel using the RC time constant changes when the panel is touched to induce pulse overlapping.

The potential for large area applications is proven by simulating a 42-inch touch panel with proper assumptions.

Introduction

Touch screen panels have attracted much attention in various applications since they can simplify the interface between human and products and change’s people life style.

Photo detection touch sensors have been revealed to be sensitive to the ambient light, which easily causes sensing noise, since they determine the touch signal using the light reflection or absorption.

Circuit analysisFig .1

Fig. 1 shows the touch sensing unit consisted of one thin-film transistor, one capacitor, and one resistor.

In operation, when the panel is untouched, the scan pulse V scan, N-1 is firstly fed to node B and raise the voltage of node B, VB, to 10 V. At this time, the thin-film transistor does not output current because there is no voltage difference between drain and source.

Although the scan pulse V scan, N comes in and parasitic capacitance and resistance emphasize the importance of Tenable.

Fig. 2

One of the value is universal to the backplane structure, such as on-cell and in-cell, and the thin-film transistor material, such as amorphous silicon, low temperature polycrystalline silicon, and oxide thin-film transistor.

In this case, the sensing capacitor can be formed by the cover glass sandwiched in between finger and the electrode fabricated in the touch sensing array and protected by the cover glass.

Fig. 3

Fig. 4

Fig. 5

Only design process can be demonstrate from the concept of the circuit for the on-cell case, while the case of in-cell can be similarly developed.

The alternative pixel circuit is shown in Figure

Design Consideration, Procedure and Results:- There are many factors to design the large-area panel of the sensing

method, such as bus line width, size of thin-film transistor, and sensing capacitance.

The difference of total capacitance at sensing node when pixel is touched or untouched is less significant.

Flow chart

TABLE I:-SPECIFICATION OF THE DESIGNED 42 inch TOUCH PANEL

Items Specification

Panel size 42 inch

Aspect ratio 16:09

Frame rate 60 Hz

Pixel pitch 19x19mm

Pixel shape Square

Resolution 480x270

CONCLUSION A simple but novel concept of pulse overlapping detection for the active

matrix touch panel is used. The circuit can provide an excellent way of implementing large area active

matrix touch panels.

Thanking you ?